Process for the manufacture of photographic materials



, atented Feb. 9, 1943 PROCESS FOR THE PHOTUGRAP jlBla Gaspar, Hollywood, Calif., assignor to Chromogen, Nevada Incorporated, a corporation of No Drawing. Application July 19, 1940, Serial No.

346,435. In Great tain July 19, 1939 6 Glaims.

This invention relates to color photographic materials and has for its object the provision of processes for the manufacture of photographic colloids containing dye-forming substances which can be used to form filter layers or as silver halide emulsion layers especially in color photographic materials.

The process described in my prior patent application Serial Number 267,905, filed April 14, 1939, consists in the preparation of true aqueous solutions of dyes insoluble in water with the aid of wetting agents with hydrotropic properties. The solutions thus obtained are then mixed with binding agent solutions or with emulsions of binding agents, for instance, with gelatin solutions or with silver halide gelatin emulsions.

In prior patents the inventor described photographic materials for color photographic purposes containing dye components and also described processes for obtaining multicolor photographic pictures with such materials. As described in these patents, in general, insoluble components have to be converted into soluble derivatives thereof in order to facilitate'their incorporation in. the layer.

It is an object of the present invention to provide a process for incorporating water-insoluble dye-forming substances into photographic emulsions without the necessity of converting the insoluble dye-forming substances intosoluble derivatives. The process is applicable to waterinsoluble dye-forming substances, true aqueous solutions of which can be obtained by means of hydrotropic substances. The dye-forming substances may be of different kinds and may, for example, be used for the formation of azo dyes, vat dyes and in the process of so-called color developrnent.

According to the present invention, therefore, insoluble dye components are incorporated into photographic layers by forming a true aqueous solution of the dye component with the aid of a sufficient quantity of a wetting agent with hydrotropic properties, thereaftermixing the solution thus obtainedwith a binding agent solution or with an emulsion, for instance, a silver halide emulsion, using the final product to make a layer.

For carrying out this process any insoluble dye A component that can be made to form true aqueous solutions by means of hydrotropic agents is suitable. In many cases the preparation of the dye component solutions can be still further facilitated by using in addition to the hydrotropic substances organic solvents that are miscible with water, such as methyl alcohols, ethyl alcohol, acetone, dioxane, pyridine or diacetine in small quantities.

The term, "hydrotropic Wetting agents is used inthis specification to denote salts of a polar constitution such as the alkali salts of alkylated or aralkylated naphthalene sulphomc acids, or of benzyl sulphanilic acid, or of other organic acids such as enumerated by Ullman in Encyclopaedie der Technischen Chemie, 2nd edition, vol. E, page 808, which are capable of multiplying the water solubility of difficult. soluble compounds, especially such organic compounds.

In practicing the process of the present invention, the hydrotropic wetting agents enumerated as examples in my co-pending patent application No. 14,068/38 may be used. These include the sulphuric acid ester of the butyric ester of ricinolic acid (known as Avirol AH, made by H. Th. BoehmeAvirol is a registered trademark), the sodium salt of sulphonated castor oil (known as Monopol Soap, manufactured by Chemische Fabrik Stockhausen & Co.-Monopol is a registered trade-mark), Sapamine MS (a special basic fatty acid amide manufactured by the Society for'Chemical Industry in Basle Sapamine is a registered trade-mark) and Nekal BX (a special alkylated naphthalene sulphonic acid manufactured by the I. G. Far-benindustrie A. G.Nekal is a registered trademark).

In addition to these, compounds acting similarly may also be used, such as Nekal AEM (a mixture of the sodium salt of a special alkylated naphthalene sulphonic acid with glue manufactured by I. G. Farbenindustrie A. G), and the Igepones (special fatty acid derivatives manufactured by the I. G. Farbenindustrie A. G.- Igepone is a registered trade-mark).

2 grams of Nekal AEM and 0.5 cc. of pyridine are dissolved in 5 cos. of water. To this solution there is added an aqueous solution of 0.3 gram of dinaphthole. After filtering off a small undissolved residue, a clear solution of the dye component is obtained. Thereupon 15 cos. of a 20% gelatin solution is thoroughly mixed with the solution of the dye component. The slightly alkaline solution is neutralized with acetic acid, and after solidifying, the gelatin ispreferably washed.

The gelatin containing the dye component is thereafter thoroughly mixed with an equal amount of silver halide gelatin emulsion to yield a light-sensitive emulsion suificient to cover 0.3 sq. metre,

The light-sensitive layer containing the dye component may then be used for the. production of a dye-image in a multi-layer material. The process employed for obtaining the dyeimage may be the known process of the local destrustion of the dye component depending on a silver image produced in the layer, and afterwards forming an azo dye from the dye component remaining in the layer; or converting the dye component to an azo dye uniformly throughout the layer and afterwards destroying the dye locally in dependence on the silver image. On coupling with diazotized sulphanilic acid, for instance, the dinaphthole yields an orange azo dye.

Similarly the layer maybe used in a material for the process of so-called color development in which case the dinaphthole serves as a coupling component for color development yielding a blue dye with the ordinary colo'r developers.

Silver halide emulsions prepared according to the process described above can be sensitized in the usual manner by adding sensitizers at any stage of their preparation.

A multi-layer material for color photographic purposes can be prepared by superimposing silver halide emulsions prepared in accordance with the invention.

I claim:

l. A process for producing layers for photographic purposes which comprises dissolving a dye-forming substance which is substantially insoluble in water in a solution comprising water and a quantity of a hydrotropic substance sufficient to form a true solution, incorporating a binding agent in said solution and then forming said solution into a layer.

2. A process for producing layers for photographic piu'poses which comprises dissolving a dye-forming substance which is substantially insoluble in water in a solution comprising water and a quantity of a hydrotropic substance sumcient to form a true solution, incorporating a colloid solution in said solution and then form-- ing said solution'into a layer.

3. A' process for producing layers for photographic purposes which comprises dissolving a dye-forming substance which is substantially insoluble in water in a solution comprising water and a quantity of a hydrotropic substance sufficient to form a true solution, adding a silver halide emulsion 'to said solution and then forming said solution into a layer.

4. A process for producing layers for photographic purposes which comprises dissolving a dye-forming substance which is substantially insoluble in water in a solution comprising water and a quantity of a hydrotropic substance sufiicient to form a true solution, incorporating a ,bindingagent and a light-sensitive silver halide insaid solution and then forming said solution into a layer.

5. A process for producing layers for photographic purposes which comprises dissolving a dye-forming substance which is substantially insoluble in water in a solution comprising water and a quantity of a hydrotropic substance sufiiv cient to form a true solution, adding a silver halide gelatin emulsion to said solution and then forming said emulsion containing the dye-forming substance into a layer.

6. A process for producing layers for photographic purposes which comprises dissolving a dye-forming substance which is substantially insoluble in water in a solution comprising water and a quantity of a hydrotropic substance sufflcient to form a true solution, incorporating a silver halide gelatin emulsion and a sensitizing dye in said solution and then forming said solution into a color sensitized light-sensitive layer.

BELA GAsPAR. 

